to look up the correct name

There are two kinds of alveolar fricatives in English: voiceless /þ/ as in thin and voiced /ð/ as in that. The name of the first character is thorn and that of the second one is edh. Voicing is a rather common distinctive feature in many languages. The stops /p/, /t/, and /k/ are voiceless, and /b/, /d/, and /g/ are their voiced counterparts. Usual the term hard is used to distinguish fricatives or affricates from stops: e.g., the g in gel from that in goat.

Many languages borrow words with no intention of paying back the loan. It's one of the ways that languages get new vocabulary.

Ceci n'est pas un seing.