Definition
Indicates that the speaker cannot answer their interrogator's question, because of lack of experience with or knowledge on the topic.
Origins
Originally used as I only work here since at least the 1950s.
How People Actually Use It
Something you tell someone to confuse them or annoy them.
"Karen: "You're being disrespectful. You need to learn some manners😠" You:"....idk I just work here😐" Karen:"....what do you mean you just work here???😡""
Source: Urban Dictionary