Have it in for.

I posted this to Wordorigins, but I’m still unsatisfied, so I thought I’d see if the Hattery could provide enlightenment: My wife asked me about the phrase “have it in for (someone),” and I realized it is in fact a very weird construction. The OED says: P.1.e. colloquial. to have it in for: to intend revenge on; to be determined to harm or cause trouble for; to feel hostility or strong dislike towards. Cf. in for at in adv. Phrases P.2. First citation: 1825 Didn’t I owe the Major an ould grudge..? I had it in for him. Captain Rock in London 17 September 226/3 But their “Cf. in for” isn’t any help; that phrase is defined as “Involved in some coming event, etc., esp. one which cannot be avoided; finally committed to do something; (now esp.) destined to experience something,” which doesn’t seem to have much relevance — and in any case, how does the phrase “have it in for” work? Any thoughts? (I know idioms are not transparent, and maybe this one is inexplicable, but I thought I’d ask.)…