fens

The root fens comes from Latin -fendere (past participle -fensus), meaning 'to strike, to hit.' Here is the strange part: this verb never existed on its own. There was no Latin word fendere meaning simply 'to strike.' It only ever survived locked inside compounds, where a prefix tells you which direction the blow goes.

Two prefixes did almost all the work:

- dē- (away, off) + fendere = dēfendere: to strike the attacker away from you. That is exactly what defense is — beating back a blow. From this we get defend (to ward off attack, and by extension to argue for someone in court — beating back the accusation) and defensive (in the posture of warding off). The legal sense gave us defendant: literally 'the one being struck at,' the person under attack in a lawsuit, who must defend themselves.

- ob- (toward, against) + fendere = offendere: to strike toward or into someone. To strike at a person is to hurt or insult them — so offend means to upset, offensive means hurtful (or, in war, attacking), and offence/offense is the blow itself: a crime, an insult, or a military attack.

The most surprising members are two clippings of defence. When medieval English shortened defence down to its tail, it produced fence — first meaning 'defense,' then the physical wall that does the defending, then just any barrier. The same word, used for the art of sword-defense, became fencing — the sport of attack and parry with a blade. So one short word carries both halves of the root's meaning: the wall that keeps blows out, and the swordplay that trades them.

Finally, fend is defend with its head chopped off. To 'fend off' an attack keeps the original sense (strike it away), while to 'fend for yourself' means to defend your own survival — to look after yourself with no one else guarding you.

The pattern to remember: fendere is a hidden striker. You never meet it alone — only as defend, offend, fence, fend. Read the prefix and you know where the blow lands: dē- strikes it away, ob- strikes it toward you.