A quick note: there are inconsistencies in this puzzle’s theme that testers were very divided on. Some didn’t care about them at all, but others felt they ruined the puzzle. I do think the theme is fun, but wanted to add this quick disclaimer first!
The theme involves taking (imagined) numerical prefixes literally: UNINTERESTING, BIG EGO, TRIPWIRE, TETRIS, and PENT UP ("root n"). The inconsistencies are that uni-, bi-, and tri- are Latin roots, while tetr- and pent- are Greek (this is because there are simply no good options that I found for quad- and quint-) and also that the vowel is included as part of the Latin roots but not the Greek ones. Anyway, now you know.