To determine the text origin from a given GUI element, I think the fastest solution is to use the developer tools: in transaction SE51 (dynpros), enter the dynpro name, display the attributes of the tab buttons. If it's a text, then it's a simple translation of the dynpro (SCRT). If it's a variable name, then you should go to transaction SE38, enter the program name, and search how this variable is setup. Possibly, it comes from a text element, so you need to translate them (REPT).
I don't think you can find the terms easily using SE63, but I'm quite novice with the translation concept.
After the translations, I think you need to regenerate the dynpro load for SCRT (program RSLANG20) and the program load for REPT (transaction SGEN).