Dear etaoin: a jalopy is an automobile that has had the sxxx knocked out of it, but not by jalap.
Just for the hell of it, I tried to see if I could find
etymology of jalopy. No luck, but I did find an interesting
word:

Source: Webster's Revised Unabridged Dictionary (1913)

Jactitation \Jac"ti*ta"tion\, n. [L. jactitare to utter in
public, from jactare. See Jactancy.]
1. (Law) Vain boasting or assertions repeated to the
prejudice of another's right; false claim. --Mozley & W.

2. (Med.) A frequent tossing or moving of the body;
restlessness, as in delirium. --Dunglison.

Jactitation of marriage (Eng. Eccl. Law), a giving out or
boasting by a party that he or she is married to another,
whereby a common reputation of their matrimony may ensue.
--Blackstone