ram + rod

Ramrod is a compound: ram (from Old English ramm, a male sheep, extended to mean 'a device for forcing or pushing') plus rod (from Old English rodd, a slender stick). The word appeared in the early 1700s for the tool used to push a lead ball and powder charge down the barrel of a muzzle-loading musket. Without the ramrod, the musket could not be loaded. It was the most essential accessory of the most common weapon.

Speed with the ramrod determined battlefield effectiveness. A trained British soldier could load and fire his Brown Bess musket three times per minute. Much of that speed depended on the ramrod — drawing it from the barrel housing, seating the ball, returning the ramrod, and raising the musket to fire. The ramrod was a soldier's constant companion, and it was fragile: a dropped ramrod on a battlefield could mean death, because the musket became a club without it.

By the mid-1800s, breech-loading rifles made the ramrod obsolete. The tool disappeared from military use within a generation. But the metaphor survived. 'Ramrod straight' — meaning perfectly upright, rigid, unbending — appeared by the 1830s. 'To ramrod something through' — meaning to force it through by sheer will — appeared by the early 1900s. The tool died. The metaphors multiplied.

The word now exists almost entirely as a figure of speech. A ramrod is a person who enforces discipline rigidly. A ramrod posture is perfectly straight. To ramrod legislation through Congress is to push it through without compromise. The physical object — a thin metal or wooden rod about three feet long — is found only in Civil War museums and muzzle-loader enthusiast circles. The metaphor outgrew the tool that inspired it.