lack (n.)

c. 1300, "absence, want; shortage, deficiency," not found in Old English, of uncertain origin. Perhaps it is from an unrecorded Old English *lac, or else borrowed from Middle Dutch lak "deficiency, fault;" in either case probably from Proto-Germanic *lek- (source also of Old Frisian lek "disadvantage, damage," Old Norse lakr "lacking" (in quality), "deficient" (in weight)), from PIE *leg- (2) "to dribble, trickle" (see leak (v.)). Middle English also had lackless "without blame or fault."

lack (v.)

"be wanting or deficient" (intransitive), late 12c., perhaps from Middle Dutch laken "to be wanting," from lak (n.) "deficiency, fault," or an unrecorded native cognate word (see lack (n.)). Transitive sense "be in want of" is from early 13c. Related: Lacked; lacking.

To lack is primarily and generally to be without, that which is lacked being generally some one thing, and a thing which is desirable, although generally not necessary or very important. [Century Dictionary]

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Definitions of lack from WordNet
lack (v.)
be without;
This soup lacks salt
Synonyms: miss
lack (n.)
the state of needing something that is absent or unavailable;
there is a serious lack of insight into the problem
Synonyms: deficiency / want