the.com/accretion

means The gradual growth of something through slow, successive additions of material layered on from outside, rather than one big dramatic burst.

from From Latin accretio, built on the verb accrescere — 'ad-' (toward) plus 'crescere' (to grow, the same root that gives us 'crescent' and 'increase'). Romans used it literally: a river silting up its banks grain by grain. English borrowed the word in that same patient, particle-by-particle spirit, later lending it to geologists describing continents and astronomers describing planets forming from swirling dust — nothing sudden, just matter sticking to matter until mass appears.