Green’s Dictionary of Slang

swell adj.

also swellified
[swell n.1 ; 20C+ use mainly US]
[early 19C+] (orig. US Und.)

1. excellent, wonderful, delightful; thus swell article n., anything of high quality; swell crib n., a genteel house; also ironic use.

2. pertaining to the upper classes.

3. showy, ostentatious, fashionable, usu. as regards dress; also as adv., fashionably; thus swell mollisher, a very well-dressed woman etc.

In compounds

swell cove (n.) (also swell kidder) [cove n. (1)]

a gentleman, a dandy.

swell dona (n.) [dona n. (1)]

[late 19C] a lower-class woman affecting airs of grandeur.

swell fencer (n.) [-fencer sfx; needles are required for the tailoring that garbs a swell]

[mid-19C] a street-seller of needles.

swell mob (n.)

see separate entry.

swell woman (n.) (also swelly)

[late 19C] an élite prostitute; a woman kept by a rich lover.