1740, Latin, literally "in its (original) place or position," from ablative of situs "site" (see site (n.)).
Entries linking to in situ
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").
situ
see in situ.
situs n.
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).