manager promoted from in-house office worker
Refers to a company president or top manager who rose through the ranks from a regular salaried employee, often implying a non-founder, non-family successor.
As a manager promoted from the ranks, he understands the hardships of the front line well.
That company is run by a manager who came up through the company, not by the founder's family.
Compound of サラリーマン (salaried worker) and 社長 (company president). The term describes a president who was promoted from within the company rather than being a founder or outside hire.