Green’s Dictionary of Slang

napkin n.

SE in slang uses

In compounds

napkin ring (n.)

(US gay) a penis ring.

1972		B. Rodgers Queens’ Vernacular 140: napkin ring (kwn SF, SM sl, ’70) metal or leather hoop pulled over the penis and testicles.
1999		Gaymart.com Queer Sl. in the Gay 90s 🌐 Napkin Ring – A cock ring.

napkin snatching (n.)

stealing handkerchiefs.

1823

Egan Grose’s Classical Dict. of the Vulgar Tongue.

In phrases