Questionable origins: allegedly MO's inscription in someone's TKD (source unknown). "Krankor confided to me at the Las Vegas qep'a' (javDIch?) that *he* (Krankor) made it up, in the early days of the old mailing list (run by Elias Israel). He said that, back in those days, there wasn't as much awareness or concern about not making stuff up, and that this is one usage/convention that has persisted through to this day." (Holtej [7/26/2005])

KGT 159: The nonslang term for an expert is po'wI' (literally, "one who is expert, skilled").

If you want to avoid controversy use pab po'wI' or *pab pIn - using the slang term pIn "expert, authority" (which I think sounds better). Also, Okrand sometimes uses this inscription when he signs books:

tlhIngan Hol jatlhwI' po'