Where does “linen tester” come from?

linen tester (English) comes from English tester, from English Test, from German testen, from German Test, from English test, from Middle English teste, from Old French teste, from Latin testis — to stand.

linen tester (English): A folding magnifying glass which, when unfolded, forms a frame for the lens at a pre-focussed distance. Commonly used in stamp collecting

Definitions

  1. A folding magnifying glass which, when unfolded, forms a frame for the lens at a pre-focussed distance. Commonly used in stamp collecting

Ancestry of “linen tester”, step by step

linen tester traces back through two separate lines of ancestry.

via English tester

StepLanguageWordMeaning
1EnglishtesterA canopy over a bed; Something that overhangs...
2EnglishTesta Test match
3Germantestento test
4GermanTesttest; melting pot
5EnglishtestA challenge, trial; A cupel or cupelling hearth...
6Middle Englishteste
7Old Frenchtestehead
8Latintestiswitness; one who testifies or attests; testicle
9Latinterstis
10Latintrīstissad, unhappy, melancholy, morose
11Proto-Indo-Europeantristh₂sa third party standing, after the two parties to...
12Proto-Indo-Europeansteh₂-to stand

via English linen

StepLanguageWordMeaning
1EnglishlinenThread or cloth made from flax fiber; Domestic...
2Middle EnglishlynnenMade of flax fibers; linen
3Old Englishlīnenlinen", "made of flax
4Proto-Germaniclīnīnazlinen, made of flax
5Proto-Germaniclīnąflax
6Proto-Indo-Europeanlīno-flax
Every word from Proto-Indo-European steh₂-