mid 16th century: from Latin congratulat- ‘congratulated’, from the verb congratulari, from con- ‘with’ + gratulari ‘show joy’ (from gratus ‘pleasing’)
16世紀半ば:ラテン語のcon- 'with' + gratulari 'show joy' (gratus 'pleasing' から)の動詞congratulariから、'congrat'された.