[brabel]

This kind of phrase usually has a historical origin.

I tried to find out what it is for "show up" but apparently, this is a very recent one and originally meant something else entirely:

"verbal phrase, by 1826 as "to disgrace through exposure;"

It then changed to the current meaning only in around 1888, just ~135 years ago:

"The meaning "to put in an appearance, be (merely) present" is by 1888."

Unfortunately, I couldn't find any explanation based on historical use of the phrase (phrasal verb, to be accurate), but given it's a quite recent one, it probably originated from people just trying to emphasize "completion" of the "show" action by adding "up", like with most other phrasal verbs.

Source: https://www.etymonline.com/word/show%20up

[chris_st]

Thanks! Yes, I remember reading older novels (Austen, maybe?) where the "disgrace through exposure" sense was used... it was obvious what was meant, but surprising.

[IIsi50MHz]

"disgrace through superior performance" is a current meaning. AA does a thing, and then (especially if AA appears to be getting praise for it or appears proud of it), BB either does it better or does something more difficult (usually accompanied by a derisive remark about AA or AA's work).