English teetering (ON titra, Ger. zittern) sounds almost the same as Serbian titranje (teetering, vibration, oscillation, seesaw, tottering).
Is guitar (Gr. κιθάρα, Sp. guittara) related to teeter?
In Serbian the history of the word titranje is completely transparent: it comes from the Hor-Gon basis, which primal meaning is "circle"; i.e. krug (circle) => kruženje (circulation; kretanje movement) => građenje (build; Slav. grad/gorad city; in fact encircling, encircled area, the same logic as in case of Eng. enclosure).

Serbian non rad (work) is derived from the verb graditi (build) and u(h)raditi (from ugraditi built in). On the other hand, Serbian ugraditi originated from the gon- prefixed Hor-Gon basis; i.e. from Gon-Hor-Gon. What are the main acts of applying force in order to build a habitat? First, is it not striking/hitting (Serb. udaranje; Slovak udrieť), pushing (Serb. guranje) and driving (Serb. teranje)? All these tree words (udaranje, guranje, teranje) have the same parent - the Serbian word ugradnja (construction; verb. ugraditi to build in, embed). If we take a more careful look at the English word construction, we can see the similar develpment, beginning with the ur-basis Gon-Hor-Gon (or rather Gon-Xur-Gon; con-stru-ing, stri-king; Serb. s-krojiti to tailor, mold; u-strojiti to build, to construct).

Now we are coming to the main point. Guitar is a stringed instrument and in order to produce the tones one has to strike (Serb. udarati) its strings (Serb. strune). The Serbian word strune (strings) is related to the above-mentioned strojenje (constructing; from skrojenje/skrajanje molding, tailoring, carpentering) and other Serbian words as striganje (shearing, fleecing), škare (scissors), stroj (machine). Striking (Serb. udar) always causes teetering (Serb. titranje) as well as tearing (Serb. trganje) and tremble (Serb. drmanje, trema).

Finally, there is the Serbian word dodir (touch), which has obviously understood as a small udar (hit, strike, beat; udaranje <= hudaranje <= hu(n)hara-gne <= Gon-Hor-Gon basis). The erbian syntagm "udarati u strune/žice" (strike the strings) has the same meaning as the word "play" (Serb. svirati).