エス語 is read as えすご (esugo) and means Esperanto.
えすご
esugo
にほんご
Japanese (language)
こくご
Japanese language (esp. as a school subject in Japan)
がいこくご
foreign language
ご
language
がいらいご
loanword (in Japanese, esp. those of Western origin)
ぼこくご
language of one's country
いちご
one word
みだしご
headword (in a dictionary)
ちゅうごくご
Chinese (language)
らてんご
Latin (language)
どいつご
German (language)
すぺいんご
Spanish (language)