1780-90; compare Scotsdink neatly dressed, trim (of obscure origin); sense shift perhaps: trim > dainty > small > insignificant; see -y1
Examples from the web for dinky
dinky little velvet-covered buttons are not for you.
It may seem crazy, but it was running a dinky club that set me on the path to seeing myself as someone who could run a business.
But its dinky little shell is inside the big, slippery body, so a sea hare can't pull back into its shell for protection.
These are not your dinky, wrapped in plastic, grocery story caramel apples.
British Dictionary definitions for dinky
dinky
/ˈdɪŋkɪ/
adjective (informal) dinkier, dinkiest
1.
(Brit) small and neat; dainty
2.
(US) inconsequential; insignificant
Word Origin
C18 (in the sense: dainty): from dink
Word Origin and History for dinky
adj.
1788 "neat, trim, dainty, small," from Scottish dialectal dink "finely dressed, trim" (c.1500), of unknown origin. Modern sense is 1850s.
Slang definitions & phrases for dinky
dinky
adjective
Small; undersized The earliest sense meant ''small, neat, trim,'' and is related to later college use dink, ''a dude'': a dinky foreign car/ dinky little town
Inadequate; substandard: What a dinky joint!(1788+)