spy (v.) Look up spy at Dictionary.com
mid-13c., "to watch stealthily," from Old French espiier "observe, watch closely, spy on, find out," probably from Frankish *spehon or some other Germanic source, from Proto-Germanic *spehon- (cognates: Old High German *spehon "to look out for, scout, spy," German spähen "to spy," Middle Dutch spien), the Germanic survivals of the productive PIE root *spek- "to look, observe" (see scope (n.1)). Old English had spyrian "make a track, go, pursue; ask about, investigate," also a noun spyrigend "investigator, inquirer." Italian spiare, Spanish espiar also are Germanic loan-words. Meaning "to catch sight of" is from c.1300. Children's game I spy so called by 1946.
spy (n.) Look up spy at Dictionary.com
mid-13c., "one who spies on another," from Old French espie "spy, look-out, scout" (Modern French épie), probably from a Germanic source related to spy (v.).