Where did "I tend to agree." as a standalone statement originate?

And what does it mean? When I first started hearing someone using it a few years ago, I figured it was a personal spin on "agree sometimes", but apparently, he's not the only one who uses this phrase.

Edit: Clarified to indicate that "I tend to agree that/with..." makes complete sense. It's when people say, "I tend to agree.", period. That's what strikes me as strange to say.

Solution 1:

Tend means "be inclined", "feel willing or favorably disposed".

She tends to believe I can get that job.

The origin of the word is middle 14th century, from the Old French tendre.

Solution 2:

It isn't so much 'agree sometimes' as 'agree somewhat' - often with an undertone of reluctance to agree. It can, obviously, depend on context.

• I tend to agree with the people who resist raising taxes.
• I tend to agree that the club should incur the expense, but I'm not completely sure yet.