The word that moved house

'Nice' once meant foolish. Before that, in Latin, it meant not knowing. Its journey to the compliment it is today took six hundred years and passed through 'precise', which is why an older book can describe a nice distinction and mean a fine one.

Semantic shift of this kind is ordinary rather than exceptional, and it moves in recognisable directions. Words narrow: 'meat' once meant food of any sort, and survives in 'sweetmeat'. Words widen: 'journey' was a day's travel, from the French for day. Words rise: a 'knight' was a servant boy. Words fall: 'villain' was a farm worker. Once you know the four patterns, a surprising number of odd modern spellings and idioms become legible.

The mechanism is not confusion. Most shifts begin as a deliberate stretch by a particular group of speakers, used because the stretch is vivid, and become invisible once a generation grows up hearing only the new sense. The speed depends on how often the word is used: frequent words shift slowly, because everyone has a stake in their meaning, while specialist terms can turn completely in twenty years.

This matters for reading older texts, where the danger is not the word you do not know but the word you think you do. A reader who stops at an unfamiliar term looks it up. A reader who meets 'nice' in 1810 reads straight past it and takes away the wrong sentence.

The habit worth building is a small suspicion of easy words in old books. If a familiar word makes a sentence slightly strange, the problem is usually not the writer.