IPA: /ʌpˈtaɪt.nəs/
KK: /ʌpˈtaɪt.nəs/
The condition of being anxious, tense, or overly concerned about things.
Her uptightness made it difficult for her to relax during the vacation.
Uptightness is formed from "up" (meaning in a higher position or state) and "tight" (from Old English "tihht", meaning firmly held or constrained) with the suffix "-ness" (meaning the state or quality of). The word describes the state of being in a tense or constrained position, both physically and emotionally.
Think of being in a 'higher' ('up') state of being 'firmly held' ('tight') — that's why uptightness means being in a tense or constrained state.