Latin, "situation, position" (see site (n.)), used in English in certain technical writings (botany, archaeology, etc.) to indicate "proper or original position and location of something" (compare in situ).
Entries linking to situs
site n.
"place or position occupied by something," especially with reference to environment, also "land on which a building stands, location of a village," late 14c., from Anglo-French site, Old French site "place, site; position," and directly from Latin situs "a place, position, situation, location, station; idleness, sloth, inactivity; forgetfulness; the effects of neglect," from past participle of sinere "let, leave alone, permit" (from PIE *si-tu-, from root *tkei- "to settle, dwell, be home").
in situ
1740, Latin, literally "in its (original) place or position," from ablative of situs "site" (see site (n.)).
*tkei-
Proto-Indo-European root meaning "to settle, dwell, be home."
It forms all or part of: Amphictyonic; hamlet; hangar; haunt; home; site; situate; situation; situs.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit kseti "abides, dwells;" Armenian shen "inhabited;" Greek kome, Lithuanian kaimas "village;" Old Church Slavonic semija "domestic servants;" Old English ham "dwelling place, house, abode," German heim "home," Gothic haims "village."