Not entirely but i could guess. Our fingerprints, in general, are used for acceptance, verification and approval of ("relevant things").
By giving your "thumbs up", it means you agree whatever being presented to you!

Here on Authicles, it's about liking to authentic posts.
@ANTIBODY
@Tosu

100% It's a symbol of endorsement. So you don't just like, you endorse what you feel resonates with you. It's a reflection of how serious the content you respond to matters most to you. This is Authicles: we stand for #accuracy #authenticity and #relevancy in all we do.