Picture a thin layer that is only just holding on: the paint on an old door, the top of a warm egg tart, the dry skin on a hand in winter. Touch it and a piece lifts away. That is a flake, and flaky is the state of being made of them. The word's other uses keep the same feel of something that does not hold: a person who agrees to meet and then peels away, a connection that is there and then gone.
Built as flake + -y, so the core is simply 'made of, or shedding, flakes'.
這個字就是 flake（小薄片）加上 -y（帶有…的）。所以核心很單純：有薄片的、會起薄片的。
Wiktionary etymology supplied in this packet: 'From flake + -y.'
From the picture
撐不住、靠不住
把「一碰就掉一層」的感覺搬到人和機器上：看起來好好的，真要靠它的時候就脫落了。這是幫助理解的連結，不是在說歷史上哪個意思先有。
adjective · B2
Used of a person: not someone you can depend on. A flaky person forgets things, changes plans at the last minute or drops arrangements they have made, and may come across as a little odd.
靠不住的（人）
adjective · B2
Breaking, or easily broken, into small thin pieces; also made of thin layers that come apart when you touch them, the way good pastry does.
易碎成薄片的