noun
main account; primary account; real-name account
Internet slang for one's main social media account, as opposed to a sub-account (サブ垢) or anonymous account. Often implies the account tied to one's real identity.
本垢では仕事の話しかしない。
I only talk about work on my main account.
サブ垢を作って、本垢とは別の趣味を楽しんでいる。
I made a sub-account and enjoy hobbies separate from my main account.
Compound of 本 (main) and 垢 (ateji for アカ, abbreviation of アカウント 'account'). The ateji 垢 (dirt, grime) is used purely for its phonetic reading あか and has no semantic connection.