The second stem of Japanese verbs ends with an -i, so for most verbs ending in る that will be り (e.g. わかる->わかり), and for most verbs ending in す it will be し (e.g. 直す->なおし), also the verb する which is used as a formant with Chinese and 外来語 roots to form verbs has the second stem し (e.g. 勉強する->勉強し). The second stem by itself has a meaning close to the English present participle or verb noun (doing, understanding, correcting, etc.) as well as forming the ます form which is basic for neutral polite speech (e.g. 勉強し＋ます->べんきょうします).

the simple answer to the question is: no, they don't have actual meaning, just symbols of adjectives. if u wanna know further, well, the origin of Japanese is actually greatly affected by the chinese wu dialect, in Wu, we use 兮（the same pronunciation as し） to express emotions and determine the degree of the adjectives. as time goes by, some しs are gradually turned into いs. u can google some papers by using the key words like "japanese origin" "Wu dialect" or something. goodluck & have fun!