An Etymological Dictionary of Astronomy and Astrophysics

A place or building equipped for making observations of astronomical, meteorological, or other natural phenomena, especially a place provided
with a telescope for observing astronomical objects.

Etymology (EN): From Fr. observatoire, from
L. observa(re), → observe, + -toire, from L. -torius, from -tor a suffix forming agent nouns + -ius adj. suffix.

Etymology (PE): Nepâhešgâh, from nepâheš, → observation,

• -gâh suffix of place (O.Pers. gāθu-, Av. gātav-, gātu- “place, throne, spot” (Skt. gátu- “going, motion; free space for moving; place of abode,” PIE *gwem- “to go, come”).