Correct spelling for the English word "undershortses" is [ˌʌndəʃˈɔːtsiɪz], [ˌʌndəʃˈɔːtsiɪz], [ˌʌ_n_d_ə_ʃ_ˈɔː_t_s_i__ɪ_z] (IPA phonetic alphabet).
The term "undershortses" seems to be a pluralized form of "undershorts". However, "undershorts" itself is not a widely recognized or commonly used term in the English language. It may refer to a type of undergarment worn under shorts or pants for added support or coverage, similar to boxer briefs or compression shorts.
As for the etymology of "undershorts", it combines the words "under" and "shorts". "Under" indicates something below or beneath, while "shorts" refer to a type of clothing that covers the lower body but does not extend to the full length of pants. The combination suggests a garment worn underneath shorts, possibly to provide additional comfort or support.