It means literally ‘the hill of January’ in Spanish. You could render it as ‘the uphill slog/trudge of January’. The excitement of Christmas is over, we’re all tired, the yearly bills come in this month, the worst of the winter is still to come, and we’ve got to get back to work.
Nevertheless, some of my memories of January are of occasional balmy days (‘false spring’, it’s sometimes called), and a different quality in the light as the days begin to lengthen (not so you’d notice, at least not for a while).
It can’t be winter for ever.
So, a happy New Year to both our readers.