ADVERBS Presently; round; severally; sinceSince (A.-S. sith == "time," also adv.1 "late," "later;" "sith-than" == "after that") adverbially for "ago."
This must be explained by an ellipsis: “I told your lordship (it is) a year since (I told you).” Compare a transitional use of "since" between an adverb and conjunction in "Waverley; or, 'tis Sixty Years since." Omit "'tis," and since becomes an adverb. So since is used for "since then," like our "ever since" in
“I told your lordship a year since.
Since, when used adverbially as well as conjunctionally, frequently takes the verb in the simple past where we use the complete present:
“And since, methinks, I would not (do not wish to) grow so
This is in accordance with an original meaning of the word, "later," ("sith.") We should still say, "I never saw him after that;" and since has the meaning of "after." We also find the present after "since," to denote an action that is and has been going on since a certain time. (So in Latin with "jampridem.")
“I did not see him since.
See Conjunctions, 132.
“My desires e'er since pursue me.