x1 is a Lojban compound-word idiom made of four combining forms (rafsi); x1 is a "Lojbanic chengyu/yojijukugo".
vonrafpemjvo are Lojban words that imitate the structure of Chinese/Japanese/Korean four-character proverbs. The "ideal" short form is four rafsi, with no epenthetic r's, n's, or y's. Examples of these include dekpredekpu'a, zditeitortei, gekfegdripu'a, and except for the fact that it is literal and not poetic (pemci → -pem-), the word vonrafpemjvo itself.