Quirk
A quirk was a unique trait of a specific individual or device that set them apart from others of their kind.
In 2371, shortly after joining USS Voyager's crew, chief engineer B'Elanna Torres admitted that Joe Carey was more familiar with the quirks of the starship's warp engine than she was, having served on the ship prior to its Delta Quadrant exile. (VOY: "Parallax")
When leaving her engineering duties to go on her honeymoon in 2375, the Silver Blood "Torres" cautioned her replacement "Seven of Nine" that although she understood how the engine worked, she did not know its personality, adding that the engine had its own quirks and moods. (VOY: "Course: Oblivion")