The maximum segment size (MSS) is a parameter of the Options field of the TCP header that specifies the largest amount of data, specified in bytes, that a computer or communications device can receive in a single TCP segment.
[1]: §3.7.1 The IP datagram containing a TCP segment may be self-contained within a single packet, or it may be reconstructed from several fragmented pieces; either way, the MSS limit applies to the total amount of data contained in the final, reconstructed TCP segment.
[1]: §3.7.1 Small MSS values will reduce or eliminate IP fragmentation but will result in higher overhead.
For example, TCP Time Stamps are enabled by default on Linux platforms.
The two are similar in that they limit the maximum size of the payload carried by their respective protocol data unit (frame for MTU, TCP segment for MSS), and related since MSS cannot exceed the MTU for its underlying link (taking into account the overhead of any headers added by the layers below TCP).