1570s, "written on the margin," from Medieval Latin marginalis, from Latin margo (see margin). Sense of "of little effect or importance" first recorded 1887. Related: Marginally.
marginal mar·gin·al (mär'jə-nəl)adj.
Of, relating to, located at, or constituting a margin, a border, or an edge.
Marginally within a lower standard or limit of quality.
Relating to or located at the fringe of consciousness.