long ago is an adverb meaning "of the distant or comparatively distant past". It carries one recorded sense.
of the distant or comparatively distant past
“We met once long ago”
“they long ago forsook their nomadic life”
“left for work long ago”
“he has long since given up mountain climbing”
“This name has long since been forgotten”
“lang syne”
Definitions, synonyms and semantic relations for long ago come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.