Seemingly means on the surface, judging only by appearances. Seemingly endless, seemingly unrelated, seemingly by accident.
It marks the speaker's distance from the claim: seemingly means it looks that way and I am not vouching for it. Seemingly endless and seemingly unrelated are near-fixed phrases. Note apparently, which does the same job and also carries the sense of what people say; and that seemingly is a useful hedge in reporting where the writer knows how a thing looks and not why.
1adverbseeminglyOn the surface, judging only by appearances.
“The seemingly calm sea hid dangerous currents beneath the surface.”
synonyms: apparently, ostensibly
seemingly is a hedge about appearance.
Also accepted in games: apparently
The word is seem plus -ing plus -ly, all native. Seem comes from Old Norse soema, to conform or befit, and English took the verb along with a great deal of everyday vocabulary from the same source.
Middle English
semyngly
English, today
seemingly
From Middle English semyngly, equivalent to seeming + -ly.
Etymology from Wiktionary, CC BY-SA