leaf (n.) Look up leaf at Dictionary.com
Old English leaf "leaf of a plant; page of a book," from Proto-Germanic *laubaz (source also of Old Saxon lof, Old Norse lauf, Old Frisian laf, Dutch loof, Old High German loub, German Laub "foliage, leaves," Gothic lauf), perhaps from PIE *leup- "to peel off, break off" (source also of Lithuanian luobas, Old Church Slavonic lubu "bark, rind"). Extended 15c. to very thin sheets of metal (especially gold). Meaning "hinged flap on the side of a table" is from 1550s.
leaf (v.) Look up leaf at Dictionary.com
"to turn over (the pages of a book)," 1660s, from leaf (n.). The notion of a book page also is in the phrase to turn over a (new) leaf (1570s). Related: Leafed; leaved; leafing.