The name Selah means "To Pause and Reflect". Specifically used in the Psalms after a passage of scripture. You are supposed to pause and reflect on the previous passage.
I have seen SELAH used as first name in a South Carolina will dated 1787 by her father then in 1795 by her husband. This SELAH was born around 1750 either in North Carolina or South Carolina. I have been told this name is Native American often given to one named Sarah but I have not seen this confirmed anywhere. But based on family records Sarah was a common name for the related family during the period noted above.
I've been looking into this word and the consensus seems to be that, although it might well originate in music as a pause as suggested, the scriptural usage indicates an instruction to the reader to stop and consider carefully what has been said. In effect, it's a reinforcer: "reflect on the above, because it's important".