Etymology Map
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Infiltrate

2 stages from Medieval Latin to English.

Today it means to secretly enter an organization

Where does the word "infiltrate" come from? It comes from Medieval Latin filtrum, adopted directly into English (1750s).

1
Stage 1 of 2
filtrum
Medieval Latin · medieval
"felt used as a strainer"
felt was used to strain liquids; the source of 'filter', which English turned into 'infiltrate'
2
Stage 2 of 2
infiltrate
English · 1750s
"to pass through a filter"
military 'infiltration' dates from the 1900s
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Read the full story

Infiltrate’s story begins in Medieval Latin: filtrum meant “felt used as a strainer.” Felt was used to strain liquids; the source of 'filter', which English turned into 'infiltrate'. It reached English by 1750s as infiltrate. Military 'infiltration' dates from the 1900s. Today, infiltrate means to secretly enter an organization.