PWS

*watar-/*watr- - tendon (SED I No. 290; Kogan 2011: 215)

is based on Hbr. yätär, Syr. yatrā, Arb. watar-, Gez. watr, Amh. wätär (some of them with non-anatomic meanings like ‘rope’, ‘cord’, ‘bowstring’)

Hebrew
yätär - cord (HALOT 452)
Jewish Babylonian Aramaic
yitrā - the straight side of the stomach (opposite to curved side) (Jastrow 605)

Nota a very specific meaning shift. 

Syriac
yatrā - rope; bowstring; cord; beam (LSyr. 313, SL 590)
Mandaic
iatra - tendon; bowstring (MD 188)
Mandaic
iatira - bowstring (MD 188)
Arabic
watar- - tendon; string, chord (BK 2 1480, Lane 2918)
Geez
watr - sinew, cord (CDG 622)
Amharic
wätär - Achilles' tendon (AED 1537)
Harari
wɔtär - nerve, sinew, gut, tendon (EDH 162)
Gurage
wätär - nerve, sinew, gut, tendon (EDG 670)
dialects not specified