Swammerdami
Squadron Leader
I was intrigued by this comment. Semantic shifts may be much less regular than sound changes, but there are repeating patterns, and the changes may be unidirectional. For example the two changes I mentioned:Examples of sound changes and semantic shifts
Here's an example of four different English words, all meaning 'leader of a group' and cognates of each other: ... The four different initial sounds (H, K, CH, SH) are all due to regular sound changes ...
Unidirectional changes of this sort are called "implicational universals", because they tend to hold across all human languages, although one does find occasional counterexamples. The point is that linguists discovered these types of universals in the first half of the 20th century, thanks to the famous Prague School linguist, Roman Jakobson.
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But how do you know what the original sound was in the protolanguage? It is unlikely to be just any sound. If you have a knowledge of common unidirectional sound changes, you can infer the original sound by tracing back to it via implicational rules.
These words have all changed their original PIE meaning, which was 'top part of an animal's body.' Just as many sound changes are one-way streets (K can mutate to CH but seldom vice versa), so this semantic shift is one-way. To fill the gap when a word shifts from 'top of animal' to 'leader', a word for 'jug or bowl' may come to mean 'top of animal' by shape analogy (German Kopf or English 'jughead'!) The French word tête has undergone both these transitions: 'cup' [Latin testa] > 'top of animal' > 'leader.'
I haven't seen much literature on the subject of semantic implicational universals, and the reason for the phonological universals can be linked to the physical difficulties inherent in the articulation of sounds. So I would be much more skeptical that one can establish implicational universals for semantic shifts quite as convincingly as Jakobson did for sound shifts.
. . . . cup > head
. . . . head > leader
have occurred in multiple languages and, or so my intuition tells me, much less likely to occur in the opposite direction.
Here are some other semantic shifts mentioned in a Lyle Campbell textbook, observed in more than one language, and in most cases likely to be one-directional. The first three are shifts due to euphemism.
. . . . sleep/kiss/lay > copulate
. . . . medicine > poison
. . . . girl/child > prostitute
. . . . horse-rider > gentleman
. . . . silver > money
. . . . journal/daily > newspaper
. . . . cool > relax
. . . . excellency > you (polite)
Surely there are other, better, examples of common semantic shifts.