Sleeping is the present participle of sleep, from Old English slæpan ('to sleep'), from Proto-Germanic *slēpaną. The historical chain includes Old English slæpan and Proto-Germanic *slēpaną. The quoted older sense, "to sleep," supplies the immediate semantic anchor for sleeping. The formation is best read as participial and borrowed: the word sleeping carries its older form-history into a compact English lexical shape. In present English it is used as a adj, "being asleep, or temporarily inactive or dormant". Related English forms include sleep, sleeper, and asleep. The result is a adj and noun whose etymology preserves both the older form and the later English specialization.