There's a clue in the matching verb. When a youth in a pimped-up Citroën Saxo goes ‘careering' down the high street, it's not a steady progression. It's a mad dash. The French carrière, from which the word derives, meant a racecourse. The ultimate source is the Latin carrus, a wagon. In English, from the 16th century, it meant a short gallop at high speed, or a cavalry charge. It acquired its present meaning of a professional life in the 19th century.
Since then, there have been various improvements. In the mid-20th century the Americans introduced the idea of ‘career men' and ‘career girls'. But some will be more interested in a more recent idea: the ‘career break'.