Michaelr: 'Laggard' comes from 'Lag' meaning behind, hindmost, late, or tardy. Which means that the common expression 'to lag behind' is tautologous.

Interesting to see 'Lagan' as an opposite to 'Flotsam' as the usual opposite is 'Jetsam'.
Flotsam is floating goods, and Lagan is sunken goods, but the common usage has Flotsam as floating goods as a result of a shipwreck or similar, whilst Jetsam is deliberately jettisoned cargo

Nigel