訓 and 川 don't sound similar in modern Mandarin due to historical phonetic changes. They were more similar
in Old Chinese. 訓*l̥u[n]-s (W dialect: *l̥- > x- ) 川*t.l̥u[n] (MC -jwen is irregular)
Character Evolution
BronzeEarly Western Zhou~1000 BCBronzeLate Warring States~250 BCSealWarring States (Chu)475-221 BCSealWarring States (Chu)475-221 BCSealQin221-206 BCSealShuowen~100 ADClericalEastern Han25-220 ADClericalThree Kingdoms (Cao Wei)222-280 ADRegularModern