Orberg in Ch XVI of LLPSI - Line 36 gives us:
Nautae nec mari turbido nec mari tranquillo navigare volunt; itaque in portu ventum secundum opperiuntur (id est ventus qui a tergo flat). Vento secundo naves e portu egrediuntur: vela vento implentur ac naves plenis velis per mare vehuntur.
but he explains too little of this for my understanding.
1) secundus, -a, -um is an adjective meaning favourable, right? But it's the same word as second (II). I went to the dictionary to find this out.
Is this where the phrase 'second wind' comes from - but which is widely understood to mean 'second' as in following on from a first burst of energy...?? That's just a thought - or does it mean 'second' and 'favourable'...?
2) what does 'Id est ventus qui a tergo flat' mean?? Does this mean 'later' - but if it does then 'later' than what...?