Green’s Dictionary of Slang

lively, amusing; thus n. jink, an amusement.

1917		A. Brazil Madcap of the School 12: ‘The Wasp’s quite jinky to-day. Actually said “my dear” to me when I arrived’.
1917		A. Brazil Madcap of the School 51: ‘We’d a jinky time, though, first. It was worth being caught afterwards’.
1917		A. Brazil Madcap of the School 205: ‘Rather a jink!’ ventured Ardiune. ‘It’ll be queer to see rows of strangers sitting in the lecture room!’.