Probably not directly tied to its similarity to OAuth, but I'm sure the name Oath came from thousands of man hours of brand psychology assessment and audience testing. Oath is the stapled together corpses of the adtech of Verizon and AOL and was/is ridiculed for being a poor name choice, but branding decisions at corporations of that size go through so many committees and data points and marketing schlubs, who knows how it came out as Oath.

  Oath, noun - profane or obscene expression usually of surprise or anger.

It's an apt name, because it describes exactly what I say whenever I land on one of their sites.