-y1 Also -ey.
Full of; having the quality of; inclined to; apt to.
[Old English -ig, of Germanic origin.]
Adjectives in this ending divide broadly into three groups. In one they straightforwardly denote the quality of the nouns from which they derive: icy, inky, juicy, mossy, sandy, speedy, waxy. A second group are to some extent dismissive or disparaging, often with a figurative or indirect association, such as beery, boozy, dreamy, mousy, tinny. A third set indicates a close attachment or mild addiction to something, as in booky, doggy, horsy. A few are formed from verbs rather than nouns: dangly, sticky.
The origins of some are now puzzling because their sources are archaic (happy is from hap, luck or fortune; jolly from a Old Norse word related to yule); some have developed figurative senses that obscure their origin (as flighty has from flight, or shirty from shirt).
The ending is active and is often used to create informal terms which may be mildly negative in tone, frequently in an attempt to communicate some quality that might be hard otherwise to describe briefly: bacony, dancey, designery, Internetty, jargony, plasticky, tabloidy.
The rules for spelling require that this ending appears as -ey when it is attached to a noun that already ends in y—clayey from clay, skyey from sky, sprayey from spray.