Japanese baby name advice: Kotei?

Hello! I have a son who is 7 weeks old- we named him Kotaro. I know this is not a very popular name right now but we like it and decided to keep it. We call him Kotay for short- after a friend of ours with a similar name. My question is we thought to spell the nickname kotei and wonder if that had a negative connotation in Japan or if it’s neutral? I heard kotei looks like emperor- is that bad? It’s not the meaning we are choosing for him but will Japanese people think it’s a strange name? We like kotei spelling better than kotay but if it’s offensive or strange to Japanese people we can stick with kotay. (Thinking of words like sensei or Taipei with similar spelling and sound..) Thanks for your input!

Hi!,
First of all, I would like to know how you pronounce Kotaro in your way. The reason why I ask this is that there are two possible ways to pronounce this Japanese name spelled in roman characters: one is Ko(short vowel)-ta-ro(long vowel), id. Kotarō, and the other is Ko(long vowel)-ta-ro(long vowel), id. Kōtarō [the diacritical mark ¯ means that the vowel with it on is pronounced long.]
I think Kotarō sounds certainly an old fashioned one nowadays, but on the contrary, it sounds like a samurai’s name of old time. As for Kōtarō, it is not certainly à la mode either, but I don’t think it is out of date. Anyway, as you prefer the spelling Kotei to Kotay for short, you have therefore two possible pronunciations as I have said. One is Kotei, and the other is Kōtei. Kotei seems not to have any special connotation in Japanese, but Kōtei means “emperor” in Japanese when all syllables are pronounced in an even(flat) tone. When it is pronounced with a higher pitch on the first syllable, it seems no special connotation in a daily life.
In short, those two shortened name don’t have any negative connotation in Japanese. I personally find interesting calling your cherished son Kōtei (emperor).

It’s a nickname, you are free to call him as you wish.
Who cares if it sounds like 皇帝 (emperor) - that is similar to calling a daughter “princess”.

Wow thanks for the responses - hard for me to explain the pronunciation we have a friend Kotaro and he pronounces it with the emphasis on the ko-
We like that but it’s hard for Americans so we more emphasize the A - like taro root with a ko in front of it.. kotAro. (Maybe sounds like guitar-o)
We have a son named Ryo and we pronounce it more like rio - the Spanish word for river as he was born in a very powerful flood here in Colorado where we live. So we tend to spell more traditional Japanese and then pronounce more American style.
As for kotei- we emphasize the ko- maybe sounds kind of like ‘okay’. Wish I could make a voice memo here!
Great to hear your thoughts.. I had one Japanese friend say it seemed corny to him to spell it kotei but I don’t really agree... juts wanted to see some other opinions! I wouldn’t want my son to have a nickname that Japanese people were secretly laughing at or making fun of! :( thanks again for your help!

You are, of course free to name/call your child whatever you want, but to answer your question "Will Japanese people Kotei is a strange name?", they probably will, but with a big IF - they'll think it's strange if they realize your son has a Japanese name.

Since you're asking the question here, I'm assuming that neither you nor the baby's father are Japanese, nor living in Japan, and so if/when Japanese people meet your son, they won't initially think he has a Japanese name. In other words, they won't think "Oh, his name is the Japanese word Kotei, which means emperor. How strange," so much as "Oh, his name is Kotei. That must be a foreign name," and thus not connect it to Kotaro.

People in Japan would be more likely to think Kotei is a strange name if your son is/appears to be Japanese, since then they probably would connect it linguistically to the Japanese vocabulary word kotei. But while kotei does mean emperor, when people in Japan talk about the emperor of Japan, they usually don't use just the word "kotei." He's more commonly referred to as "kotei heika," "his majesty the emperor," so it's not like hearing the nickname Kotei would immediately have people thinking of the emperor of Japan. They might think of kotei pengin/emperor penguins instead. There's also the chance that if your pronunciation of "Kotei" doesn't have enough length on the o sound, people might hear it as the Japanese word for "fixed" or "set" (固定/こてい instead of 皇帝/こうてい).

On the other hand, if Japanese people do know your son's full name is Kotaro, and you call him Kotei as a nickname, they'll probably think the way you'e shortening the name is unusual. In Japan, the more common ways to shorten Kotaro would be to call him Ko, Ko-kun, or Ko-chan. For a native Japanese speaker, changing Kotaro to Kotei instead of Ko would probably feel a little like how a native English speaker would feel about changing Susan to Susa instead of Susie - sort of strange, but not shockingly so.

「We like kotei spelling better than kotay but if it’s offensive or strange to Japanese people we can stick with kotay. 」

Neither one is offensive. It's not like Japanese people will find it rude and presumptuous that your son's nickname sounds like the word for "emperor." Both will seem strange to Japanese people only if they know the entire backstory of your son's name, but unless you're introducing him as "This is my son Kotaro, but we decided to give him the nickname Kotei" most Japanese people will just think "Kotei must be a normal name in this person's home country."

Your answer is extremely helpful thank you!
You’re right we aren’t Japanese.. it’s a long story I was raised in a Japanese Buddhist lineage so we have a lot of contact with Japanese people and community... my husband is actually half Chinese so it’s a little tricky with the Japanese names! Kids don’t look totally Asian but they look mixed (I am half Israeli..) it’s funny we actually DO typically say his name is Kotaro and we call him kotei! I’m okay with not calling him Ko- something. Maybe Japanese people can just ask and we can explain but I feel fine with doing things nontraditionally i just wanted to make sure it wasn't super strange or offensive or arrogant! We also have a ryo and a zendai (they have more traditional Japanese middle names naoki and kazuyuki from a Japanese teacher as well..) I ask because we tried to name middle son Zion and we didn’t plan for all boys to have Japanese names... (ryo was born in a flood so we wanted to name him rio after the rivers he was born in - but then spelled Japanese style after a Japanese friend.. so started the Japanese name trend..) but then Zion translates poorly In Hebrew so we went with zendai instead so ended up going more Japanese route after all (also is uncommon name I know but inspired by old name zendayu .) then we didn’t want to leave 3rd son out of Japanese name also! So he got Kotaro for his formal name but we like kotei after a family friend of ours.
Does kotay spelling bring anything up for any of you as far as translation in Japanese? I know it depends on the kanji! (We pronounce like similar to coat-a.. hard to explain!) thanks so so very much for such thorough responses!!