stratagem (n.)

1810, "the art of a general, the science of war," from French stratégie (16c.) and directly from Latinized form of Greek stratēgia "office or command of a general," from stratēgos "general, commander of an army," also the title of various civil officials and magistrates, from stratos "multitude, troop, a division of the people; army, navy, expedition, encamped army," probably originally "a camping army," and meaning etymologically "that which is spread out" (from PIE *str-to-, from root *stere- "to spread"). With Greek agos "leader," from agein "to lead" (from PIE root *ag- "to drive, draw out or forth, move").

As "an instance of strategy, a particular strategy" by 1833. In non-military use by 1887.

*sterə-, also *ster-, Proto-Indo-European root meaning "to spread."

It forms all or part of: consternate; consternation; construct; construction; destroy; destruction; industry; instruct; instruction; instrument; obstruct; obstruction; perestroika; prostrate; sternum; sternocleidomastoid; strain (n.2) "race, stock, line;" stratagem; strategy; strath; strato-; stratocracy; stratography; stratosphere; stratum; stratus; straw; stray; street; strew; stroma; structure; substrate; substratum; substructure.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit strnoti "strews, throws down;" Avestan star- "to spread out, stretch out;" Greek stronymi "strew," stroma "bedding, mattress," sternon "breast, breastbone;" Latin sternere "to stretch, extend;" Old Church Slavonic stira, streti "spread," strana "area, region, country;" Russian stroji "order;" Gothic straujan, Old High German strouwen, Old English streowian "to sprinkle, strew;" Old English streon "strain," streaw "straw, that which is scattered;" Old High German stirna "forehead," strala "arrow, lightning bolt;" Old Irish fo-sernaim "spread out," srath "a wide river valley;" Welsh srat "plain."