バイバイ

From English bye-bye. Attested from at least the 1930s.^[1]

• (Tokyo) バイバイ [báꜜìbàì] (Atamadaka – [1])
• IPA^(key): [ba̠iba̠i]

バイバイ • (baibai) 

1. (informal) bye-bye

バイバイ • (baibai) 

1. (informal) leave-taking, saying goodbye
   • 1968 [1962], Shōno Junzō, “Michi”, in Gendai Nihon bungaku taikei [Contemporary Japanese literature collection], page 184:

     番(ばん)頭(とう)に手(て)切(きれ)金(きん)を持(も)って来(こ)させて、それであっさりバイバイであったそうです。

     Bantō ni tekirekin o motte kosasete, sore de assari baibai de atta sō desu.

     The clerk was asked to bring out the consolation money marking their separation, and with that they made a simple goodbye.

バイバイする • (baibai suru) suru (stem バイバイし (baibai shi), past バイバイした (baibai shita))

1. (informal) to take one's leave, to say goodbye

   じゃ、祖母(ばあ)ちゃんにバイバイして。

   Ja, bāchan ni baibai shite.

   OK, say bye-bye to Grandma.

   • 2014, Nakagawa Nobuko, Kodomo no hattatsu ni awaseta okāsan no katarikake [Mother’s speech styles appropriate to children’s development], page 66:

     「そうね。昨日(きのう)、公(こう)園(えん)でネコと遊(あそ)んだね。楽(たの)しかったからバイバイするとき、さびしかったね」

     “Sō ne. Kinō, kōen de neko to asonda ne. Tanoshikatta kara baibai suru toki, sabishikatta ne”

     [Tell the child,] “That’s right. Yesterday in the park you played with a cat, didn’t you. Since it was fun, you were lonely when it was time to leave”