Both Yovel and Shavuos are the fiftieth after a cycle of 7 sets of 7 (7 Shmittas, each 7 years/ 7 weeks each 7 days) and both are after “Shabbos” - we start counting the Omer “after Shabbos”, so Shavuos is also “after Shabbos”/ Shmittah is called Shabbos, and Yovel is the year after the seventh Shmittah, so it is also “after Shabbos".
Do any of our sources discuss this connection?