WEAK, INEFFECTIVE : She can't rely on her feckless son.
WORTHLESS, IRRESPONSIBLE : a feckless maneuver that could only serve to strengthen the enemy
Someone feckless is lacking in feck. And what, you may ask, is feck?
Feck is a Scots term that means "effect" or "majority" and comes from an alteration of the Middle English effect. So something without feck is without effect, or ineffective.
In the past, feckful (meaning "efficient," "sturdy," or "powerful") made an occasional appearance. But in this case, the weak has outlived the strong: feckless is a commonly used English word, but feckful has fallen out of use.
Definition of "feckless"
WEAK, INEFFECTIVE : She can't rely on her feckless son.
WORTHLESS, IRRESPONSIBLE : a feckless maneuver that could only serve to strengthen the enemy
Someone feckless is lacking in feck. And what, you may ask, is feck?
Feck is a Scots term that means "effect" or "majority" and comes from an alteration of the Middle English effect. So something without feck is without effect, or ineffective.
In the past, feckful (meaning "efficient," "sturdy," or "powerful") made an occasional appearance. But in this case, the weak has outlived the strong: feckless is a commonly used English word, but feckful has fallen out of use.
– MERRIAM-WEBSTER'S DICTIONARY