fancy (n.) Look up fancy at Dictionary.com
mid-15c., contraction of fantasy, it took the older and longer word's sense of "inclination, whim, desire." Meaning "fans of an amusement or sport, collectively" is attested by 1735, especially (though not originally) of the prize ring. The adjective is recorded from mid-18c.
fancy (v.) Look up fancy at Dictionary.com
"take a liking to," 1540s, a contraction of fantasien "to fantasize (about)," from fantasy (n.). Meaning "to imagine" is from 1550s. Related: Fancied; fancies; fancying. Colloquial use in fancy that, etc. is recorded by 1813.