The word 'feckless' has appeared in dozens of articles over the past few days since the Shannon Matthews conviction. The Chief Constable of West Yorkshire Police Force used it, as did the Daily Telegraph, the Independent and the Guardian.
Feckless is an interesting word as it is not like most other words ending in -less; clueless means 'without a clue', hopeless 'without hope', limitless 'without limits', but feckless, 'without ...'? In fact, there is a word 'feckful' in the Oxford English Dictionary, and what's more, its definition was updated only in June of this year. The OED says it is chiefly a Scottish and northern English word meaning 'powerful, effective, efficient, vigorous'. The 1989 edition of the dictionary has no citations beyond 1811; the June 2008 update was to add several more citations (the last with the 'vigorous' sense is now a Scots citation of 1981) and also to add a whole new section. The word 'feckful' has now been given a new lease of life as a humorous term meaning 'responsible, not feckless'.
The entry for 'feckless' (also originally Scottish and northern English) was updated only in June 2008, too, as formerly the definition was 'weak, helpless and lacking vigour'. The more modern meaning of 'irresponsible, shiftless' was added earlier this year.
The OED describes 'feckless' as being made up of 'feck' plus 'less', 'feck' being an earlier word than feckful or feckless and being a variant form of 'effect'. In a linguistic process known as aphesis, the short, unstressed vowel at the beginning of the word was lost. The same process happened with esquire/squire and acute/cute.