Ego-boo is short for "ego boost."

I was running out of terms from my fan-to-English dictionary.

Kath's line is modified from Joss Whedon (spoken by Buffy just before she kills Angel to save the world), Clara's line is modified from some X-Files scribe (spoken by Mulder when some mind-controlling bastard tries to force him to shoot Scully).

I now know social security numbers actually signify location of birth, but I was just stringing random digits together to work with Internet privacy concerns, as we understood them in 1998 or so.