What does "eth" mean?

A letter (capital Ð, small ð) introduced into Old English to represent its dental fricative, then not distinguished from the letter thorn, no longer used in English but still in modern use in Icelandic, the IPA and other phonetic alphabets to represent the voiced dental fricative "th" sound as in the English word then. The letter is also used in Faroese, but is generally silent in that language.

What is a synonym for "eth"?

Common synonyms include: est, ethereum, ezh, head end power, head end power, s.

Eth

//ɛð// name, noun

name, noun ·Uncommon ·Advanced level

Definitions

Noun

1
A letter (capital Ð, small ð) introduced into Old English to represent its dental fricative, then not distinguished from the letter thorn, no longer used in English but still in modern use in Icelandic, the IPA and other phonetic alphabets to represent the voiced dental fricative "th" sound as in the English word then. The letter is also used in Faroese, but is generally silent in that language.
"In Old English manuscripts thorn and eth did not have different phonetic values but were used positionally[.]"
2
Initialism of electric train heat/heating. UK, abbreviation, alt-of, initialism