The phrase "so far" refers to the extent to which something has occurred or been done up to the present time. It indicates a limit or boundary in time or progress, suggesting that what has been achieved or experienced continues up to now and may change or progress further.
The phrase "so far" derives from the combination of "so," meaning to such a degree, and "far," originating from Old English "fǣr," meaning distant or far in space or time. Its usage in English has been established since at least the 16th century.