O.Henry tells of a lawyer with amnesia on a train with
a pharmacist, who mentions "jalap". I was dumbfounded at how much ancient information is available about this
long outdated botanical purgative.

Webster's Revised Unabridged Dictionary (1913)

Jalap \Jal"ap\, n. [F., fr. Sp. jalapa; -- so called from
Jalapa, a town in Mexico, whence it was first obtained.]
(Med.)
The tubers of the Mexican plant Ipom[oe]a purga (or
Exogonium purga), a climber much like the morning-glory.
The abstract, extract, and powder, prepared from the tubers,
are well known purgative medicines. Other species of
Ipom[oe]a yield several inferior kinds of jalap, as the I.
Orizabensis, and I. tuberosa.

False jalap, the root of Mirabilis Jalapa, four-o'clock,
or marvel of Peru.

and jalopy? as in an old, run-down car? I dpn't expect any connection, but jalap made me think of it.

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

thanks, Dr. Bill.

jactitation is an interesting word. the 2nd def caught my eye. my wife and I call that "bus ride", as in the feeling you get after being cooped up on a bus for a long time. makes you very restless.