Unbidden means coming without having been asked or invited. An unbidden guest, the thought came unbidden, unbidden tears.
It is literary and is used most about thoughts and feelings that arrive on their own, which is its real work: unbidden marks something as outside the person's control. The bidden in it is the old past participle of bid, meaning asked.
1adjectiveunbiddenComing without having been asked or invited.
“Tears came unbidden to her eyes when she heard the old song.”
unbidden is a manner.
From un- + bidden.
Etymology from Wiktionary, CC BY-SA