1710, "affected with 'the scratch,'" a skin disease, from scratch (n.1) + -y (2). Meaning "composed of scratches" is from 1827; that of "grating" is from 1866. Of sounds (especially in reproduction) from 1889. Related: Scratchiness.
1580s, "slight skin tear produced by a sharp thing," from scratch (v.). Meaning "mark or slight furrow in metal, etc." is from 1660s. American English slang sense of "money" is from 1914, of uncertain signification. Many figurative senses (such as up to scratch, originally "ready to meet one's opponent") are from sporting use for "line or mark drawn as a starting place," attested from 1778 (but the earliest use is figurative); meaning "nothing" (as in from scratch) is 1918, generalized from specific 19c. sporting sense of "starting point of a competitor who receives no odds in a handicap match." Sense in billiards is from 1850. Scratch-pad is attested from 1883.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).