It's not too often you're going to find a slang word that continues to be used for over 100 years.
From the OED:

cushty, a. (and adv.)
DRAFT ENTRY Sept. 2002
Brit. slang.
Brit. /kti/, U.S. /kti/ Forms: 19- cushti, cushty, kushti. [< Romani (in Britain and Scandinavia) kushto, kushti good, perh. influenced by CUSHY a. Cf. Hindi khush, pleasure.]
Good, wonderful; fine; brilliant. Freq. as a general term of approval or agreement. Also as adv.

[1889 A. BARRÈRE & C. G. LELAND Dict. Slang I. 528/2 Kushto, koshto, good.] 1929 E. MCCARTNEY Additions to Vol. on Slang & Idioms World War in Papers Mich. Acad. Sci., Arts & Lett. 273 Cushty, smart, good. 1937 ‘J. CURTIS’ There ain't no Justice xx. 226 Him and Tommy'd manage them cushty. 1972 Guardian 9 Oct. 16/5 ‘Kushti little trailer, you know,’ he mused. 1985 J. SULLIVAN Only Fools & Horses (1999) I. 4th Ser. Episode 5. 235 (Del is on the phone.) Del. No, no, no, everything's cushty! Yeah, no, no, no, you've got nothing to worry about! 2001 Daily Tel. 4 Apr. 22/5 Jamie Oliver has shot to culinary fame with almost indecent speed, but not everyone is a fan of his ‘cushty’ cuisine.