along

\ \ [OE] The a- in along is related to the prefix anti-, and the original notion contained in the word is of ‘extending a long way in the opposite direction’. This was the force of Old English andlang, a compound formed from and- ‘against, facing’ (whose original source was Greek anti- ‘against’) and lang ‘long’. The meaning gradually changed via simply ‘extending a long way’, through ‘continuous’ and ‘the whole length of something’ to ‘lengthwise’. At the same time the and- prefix was gradually losing its identity: by the 10th century the forms anlong and onlong were becoming established, and the 14th century saw the beginnings of modern English along.

\ \ But there is another along entirely, nowadays dialectal. Used in the phrase along of ‘with’ (as in ‘Come along o’me!’), it derives from Old English gelong ‘pertaining, dependent’. This was a compound formed from the prefix ge-, suggesting suitability, and long, of which the notions of ‘pertaining’ and ‘appropriateness’ are preserved in modern English belong.

\ \ Cf.⇒ LONG