'Subscribe' is Latin for 'write underneath' — signing at the bottom of a document became pledging support.
To arrange to receive something regularly, typically a publication or service; to sign one's name to a document in agreement; to express or feel agreement with an idea or proposal.
From Latin 'subscribere' meaning 'to write below, to sign one's name underneath,' composed of 'sub-' (under, below) and 'scribere' (to write). The original sense was literal: to write one's name at the bottom of a document to indicate assent or pledge. The modern sense of paying for regular delivery of a publication developed in the seventeenth century, from the practice of signing one's name (subscribing) to a list
The modern 'subscribe' button on YouTube and streaming platforms is a direct descendant of seventeenth-century publishing practice. When a printer wanted to gauge demand for an expensive book, he would circulate a proposal and collect the names of people who pledged to buy it — they literally subscribed (wrote their names underneath). Many early books list their subscribers in the front matter, a precursor