可笑しい

Two derivations appear to have credence.[1]

• From noun 痴 (woko → oko, “foolishness, ridiculousness, outrageousness”). The sense development would have been laughable, funny, odd.
• Similar to the formation of 床しい (yukashii, “elegant, refined, admirable; reminiscent, in accordance with”) from verb 行く (yuku, “to go”), from the sense of having a quality to make one want to go towards, from verb 招く (woku → oku, “to invite others closer, to draw others closer”). The sense development would have been inviting, amusing, funny, odd.

Considering the sense grouping, it appears that this might be a fusion of derivations, or of influence. The now-obsolete senses pertaining to interesting first arise in the late Heian period[2] and would seem to fit the latter verb derivation. There are several other adjectives with similar derivation patterns, as [VERB STEM] + -ashii or -oshii.

Meanwhile, the current senses pertaining to funny and odd first appear earlier in the Heian period[1] and would seem to fit the former noun derivation.

The spelling is an example of jukujikun (熟字訓), using the characters 可 (“-able”) + 笑 (“laugh”), likely borrowed from written Chinese 可笑 (“laughable, funny, ridiculous”).

• (Tokyo) おかし​い [òkáshíꜜì] (Nakadaka – [3])[3]
• IPA^(key): [o̞ka̠ɕiː]

可笑しい (-i inflection, hiragana おかしい, rōmaji okashii, historical hiragana をかしい)

1. funny:
   1. funny, laughable

      あのピエロの動 (うご)きは、可 (お)笑 (か)しい。

      Ano piero no ugoki wa, okashii.

      That clown's behavior is funny.

   2. strange, odd

      彼女 (かのじょ)は可 (お)笑 (か)しいけど綺 (き)麗 (れい)だ。

      Kanojo wa okashii kedo kirei da.

      She is strange but pretty.

   3. unreasonable, illogical

      追試 (ついし)をしても証 (しょう)明 (めい)できなければ、その論 (ろん)文 (ぶん)は可 (お)笑 (か)しい。

      Tsuishi o shite mo shōmei dekinakereba, sono ronbun wa okashii.

      The report is unreasonable if even the supplementary examination cannot prove it.

2. (obsolete) interesting:
   1. interesting
   2. tasteful
   3. beautiful and attractive
   4. excellent, superb

The 可笑しい spelling has become rare in modern usage, superseded by the hiragana spelling おかしい.

Similar to 小さい (chīsai, “small”) and 大きい (ōkii), this adjective also has an adnominal form 可笑しな (okashina) that only attaches to nouns, and that cannot be used as the predicate of a sentence.