Is “trained up” grammatically correct?

Question

When I hear expressions like "you need to get trained up", I think the up is, at best, superfluous and probably grammatically incorrect.

Is that the case, or does the up serve a purpose?

Answer 1

Up has numerous uses and, as the OED notes, ‘the variety . . . is so great that the adverb comes to present a number of highly divergent and even directly opposite senses’.

Your example is certainly grammatical. The OED’s definition in this sense is

To cultivate or develop (the mind, the spirit, a faculty, etc.), especially for a specified purpose; to accustom to performing a specified function. Also with up.

The use of train up isn’t new. The entry gives this supporting citation from the mid-seventeenth century:

How much more ought a Christian to train up his own heart, and accustome it this way, to be his continual remembrancer of himself.