[Language]
Dutch (NL), Spanish (ES) and probably others (not checked).

[Version number]
51.0.2704.79, but also the latest master version: 53.0.2762.0

[OS details]
Tested on Linux, but it probably happens on any OS.

[Where is the poor translation?]
1. Start Chrome with the Dutch locale:
   LANG=nl_NL.UTF-8 ./chrome --user-data-dir=/tmp/profiledir
2. Visit chrome://settings/searchEngines to find a search keyword for the next step.
3. Focus the omnibox and type a search keyword, e.g. "google.nl"
4. Look at the omnibox, in particular at the grey box at the right.
   See screenshot, "Druk op [Tabblad] om Google te doorzoeken".
   It should show "Tab" (as in the "Tab" keyboard key),
   but "Tabblad" is shown instead (as in the "Tab" UI element).

Other translations may have the same issue. I tried Spanish (LANG=es_ES.UTF-8), and found that "Pulsa [Pestaña] para buscar en Google" is shown. I don't know Spanish, but according to Wikipedia this is not the tab key, but a https://es.wikipedia.org/wiki/Pesta%C3%B1a_(inform%C3%A1tica).

(this is about the translation of IDS_APP_TAB_KEY as declared in ui/strings/ui_strings.grd)
 

Deleted: omnibox-keyword-tabblad-53.0.2762.0.png 14.3 KB

	omnibox-keyword-tabblad-53.0.2762.0.png 14.3 KB View Download