Change current text XS S L M size in variation product

Hi, in variation product -> Attribute -> Size -> Values – it already has some current selections (XS, S, M, L, XL)is it possible to change these text? I can not find it anywhere in woocommerce plugin folder? I know we can add custom but since all the products on the site have already used it and I just need to add some text before it like [:en]S[:nl].. to fix display.
if anyone know where is these current S, XS,L ,M located please help me. Thanks