Meaning

noun the property of being physically or mentally strong

noun capability in terms of personnel and materiel that affect the capacity to fight a war

noun physical energy or intensity

originFrom Middle English strengthe, from Old English strengþu (“strength”), from Proto-West Germanic *strangiþu (“strongness; strength”), equivalent to strong + -th (abstract nominal suffix). Cognate with Dutch strengte (“strength”), German Low German Strengde, Strengte (“harshness; rigidity; strictness; severity”).

Etymology from Wiktionary, CC BY-SA 3.0