Assertion: ufo | /r/HasProperty | limiting and popular term
Facets:
value: at the time
type: TEMPORAL
value: in vogue
type: LOCATION
Source sentences:
text: Ruppelt is so central to the history and study of UFOs that he was the guy who literally invented the term unidentified flying object (to differentiate any and all mysterious, hard to explain aerial phenomena from merely 'flying saucers,' which was the more limiting and popular term in vogue at the time).