soon after, presently, almost, all but, no more than, after all, (kokuji)
軅 centers on the idea of something happening soon or almost, with a sense of inevitability or limitation: soon after, presently, almost, all but, no more than, after all. It is a kokuji, so its meaning is tied to Japanese usage rather than Chinese origin.
軅 is a kokuji, created in Japan rather than derived from Chinese. It combines 身 (body) with 㕍, but the exact historical motivation for this combination is uncertain. The character likely expresses the temporal meanings through a now-obscure semantic or phonetic association.
The left side 身 (body) suggests something personal or imminent, while the right side 㕍 looks like a bird (隹) under a roof (厂), as if a bird is about to land. Together, they evoke the feeling of something about to happen soon or almost here.
For やがて, imagine a person (身) waiting under a roof (厂) for a bird (隹) to arrive, and they say 'Yagate, it will come.' The whole word 'yagate' sounds like 'ya-ga-te' and fits the scene of something happening soon.