He was really waling/whaling/wailing on that guy!

[Mister_Rik]

[QUOTE=Cosmic Relief]
If it’s playing a musical instrument, it tends to be “wailing on” or just “wailing”. This is a little sketchier… fan mags and rock rags always use this spelling, but they’re not generally considered authorities on English usage. I would probably avoid using this one at all unless I were imitating a rock musician or fan circa 1950-1970. Again, not obsolete yet, but more prevalent among the pompadour set.
[/QUOTE]

“Wailing” has been mostly replaced with “screaming”, which means pretty much the same thing. Also, it’s the instrument that is “wailing” or “screaming”, not the player (unless the instrument is a human voice).

[aldiboronti]

From the OED:

Whale, v2

[Of obscure origin. Commonly regarded as a spelling of WALE v.1, but there are difficulties of form, chronology, and meaning. Perhaps orig. = to thrash with a whalebone whip (see WHALEBONE 3b).]

1. trans. To beat, flog, thrash.
   1790 GROSE Prov. Gloss. (ed. 2), Whale, to beat with a horsewhip or pliant stick. 1801 G. HANGER Life II. 162 Whaleing a gentleman is but a vulgar revenge. 1884 ‘MARK TWAIN’ Huck. Finn iii, He used to always whale me when he was sober and could get his hands on me.

   2. transf. intr. To do something implied by the context continuously or vehemently.
      a1852 F. M. WHITCHER Widow Bedott Papers (1883) vi. 67 You remember that one that come round a spell ago a whalin’ away about human rights. 1886 Harper’s Mag. July 322/1 In tones of wrath..he whaled it at his opponent throughout the fifteen minutes alloted to him. 1897 BARRÈRE & LELAND Dict. Slang, To whale away, (Amer.), to preach, talk, or lecture away continuously or vehemently. 1908 H. DAY King Spruce xxiv, You don’t think I’ve whaled up here..to..talk about women, do you? 1915 Morning Post 1 June 4/4 They..snatched these rifles up, and whaled away at our chaps.

WALE, v1, referred to in the etymology, is a Scottish and Northern English dialect word meaning to select, to choose, to pick out.

[HMS_Irruncible]

[QUOTE=Phase42]
Also, it’s the instrument that is “wailing” or “screaming”, not the player (unless the instrument is a human voice).
[/QUOTE]

In your presriptive opinion. In actual usage, it is almost universally “He was wailing on that guitar” or “he was wailing on that solo.” Nobody ever claims that the guitar was wailing on that solo.

[BMalion]

Wale, that’s the whole nine yards.

[guizot]

[QUOTE=Sailboat]
This one bothers me. I’m not even sure if it’s slang
[/QUOTE]
Yes, it’s slang. That was the whole point of the Onion article. It’s a word used only in a certain community, in informal situations. But slang words still have etymology. Often, though, they have more than one spelling.

[brujaja]

[QUOTE=Cosmic Relief]
In your presriptive opinion. In actual usage, it is almost universally “He was wailing on that guitar” or “he was wailing on that solo.” Nobody ever claims that the guitar was wailing on that solo.
[/QUOTE]

Redeemed.