what did the verb thrash originally mean?
Thrash(the noun) was a word used for punk/hardcore based music and culture(and it was also used to describe "Skate culture", skate boarders and probably skatepunk too). Thrash METAL(key word being metal) is a term for speed metal/hardcore punk oriented styles mixing(Venom, Slayer, Metallica, Bathory)
Thrash music and culture + Heavy and speed Metal and culture = Thrash metal.
More then that, the term came to mean so much more. It is like trying to debunk "dude" as a friendly noun for a male, because it was originally related to bovine cattle farms(and according to lore, infected hairs on the...).
as for the verb -
Main Entry: 1thrash
Etymology: alteration of thresh
1 : to separate the seeds of from the husks and straw by beating : THRESH 1
2 a : to beat soundly with or as if with a stick or whip : FLOG b : to defeat decisively or severely <thrashed the visiting team>
3 : to swing, beat, or strike in the manner of a rapidly moving flail <thrashing his arms>
4 a : to go over again and again <thrash the matter over inconclusively> b : to hammer out : FORGE <thrash out a plan>
1 : THRESH 1
2 : to deal blows or strokes like one using a flail or whip
3 : to move or stir about violently : toss about <thrash in bed with a fever>
synonym see SWING
...I think thrash metal has more in common with that then hardcore punk.
Its not as if the original meaning of the verb as any relevance to the debate anyway. Whats next, negating the Goth metal genre because of the original meaning of "Goth"...lmfao.