Green’s Dictionary of Slang

acid n.2

[SE acid tongue]

[20C+] cheek, sarcasm.

In compounds

acid drop (n.) [the sourness of the sweet]

[1900s] an unpleasant, ill-tempered person.

In phrases

come the (old) acid (v.) (also come the acid drop)

[1910s+] to act contrarily, aggressively, to argue; to be unpleasant or offensive, to speak in a caustic or sarcastic manner, sometimes with affection.

put the acid in (v.) (also put in the acid)

[1950s–70s] to inform on, to tell tales about, to poison someone’s mind against.

put the acid on (v.)

1. [1900s] (Aus.) to render impoverished; thus acid school, a gambling venue that takes its clients’ cash (prob. via cheating) .

2. [20C+] (Aus.) to exert pressure on a person for a loan, a favour, sexual compliance etc [supposedly orig. used by gold assayers who tested ‘real’ gold with acid].

3. [1910s] to speak sarcastically, aggressively.

4. [1910s] to put a stop to.

5. [1910s] to confirm.

6. [1910s–20s] to test out a person or statement.

stand the acid (v.)

[1900s–20s] (US) to stand up under pressure, to maintain one’s composure.

take the acid off (v.)

[1910s] (Aus.) to speak honestly, without sarcasm.