わい

Generally regarded as a shift from わし (washi), itself from 私 (watashi, “I, me”).^[1][2] First cited in a text from 1920,^[1] but likely older.

The second-person sense of you likely arose via the same general indirection mechanisms that gave rise to all Japanese personal pronouns. Consider also ancient 汝 (na) or more modern 己 (onore), used for both first- and second-person referral. This usage is first cited in a text from 1923,^[1] but is likely older.

• (Tokyo) わい [wàí] (Heiban – [0])^[2]
• IPA^(key): [β̞a̠i]

わい • (wai) 

1. (dialect, Kansai, Kagoshima; also Internet slang, originally 2channel slang) I, me (first-person pronoun, mainly used by males)
2. you (second-person pronoun, used when addressing an equal or inferior)

   Synonym: お前 (omae)

• When used as Internet slang, it was originally used by 2channel Nan-J users who habitually affect a fake Kansai accent.

See い (i).

わい • (wai) 

1. (dated or dialectal) A particle used in the end of sentences to indicate admiration or emotion. Slightly stronger than わ (wa).

Mainly used during the Edo period. Now only used by elderly males or in dialectal speech.

• だい (dai)
• かい (kai)

The reading of various kanji.

わい • (wai) 

1. 歪: askew; crooked
2. 猥: obscene; lewd
3. 隈: corner; nook; recess; inlet
4. 矮: low; short
5. 賄: bribe
6. 穢: dirty