The name Blisworth has had many variations in the past.

We find in " The Place Names of Northamptonshire " the following forms : In Domesday Book (1086) Blidesworde, and in later versions of the name from other records Bliswurda (1162), Bliseworthe (1166), Blideswurda (1184), Blieswurth (1199), Blitheworth (1200), Blicheworth (1215), Blidesworth (1216), Blethesworthe (1220), Blidewurd (1220), Bliheswurth (1242), Blecchesworth (1284), Blysworth (1317), Bleseworth (1337), Blayseweurthe (1348), Bluseworthe (1362), Bleseworth (1388), Blyseworthe (1400), Blisworth (1428), Blissworth (1791).

Domesday (1086) is the earliest date for a document mentioning our village though it seems increasingly likely that Romans (50 - 410AD) settled here as, probably, did the  Romano-British (400 - 700AD) before the influx of the Anglo-Saxons and Vikings who created the name.  
The part of the name "Blide" is a present Orkney dialect word and is pronounced b-l-i-t-h.  Our regular English word blithe comes from the same source and means happy or carefree.  The OE dictionary indicates its origin as Old English from Germanic (ie. possibly Viking).  The Orcadian word means health or wellbeing so the name of the place before 1066 seems to be a Viking name that conveys somewhere that is happy or healthy.

The more usual interpretation of the 1066 name, for example as stated by the "Place Names Society" at Nottingham University, is that it was the name of a settlement belonging to Blide or Blida because the -s- suggests a possession.  Unfortunately there is a too willing a tendency to take this path in interpretation which should apply only in cases where the name (eg. Blida) definitely appears in some other document.  If we resort to Ekwall's Concise Oxford Dictionary of English Place Names, 1964 Ed., and take all the given ramifications, the first part of the compound may be Blip or Blipe (pronounced blith) from the discussion on Bledisloe, bleap (pronounced bleath and meaning timid or sluggish) from Blaston. Then there is any of the above as a personal name - this from Blidworth (Notts) and finally blipe from any of the variations of Blyth (often rivers) meaning gentle or merry and approximating to the Orcadian usage; being applied to rivers suggests a poetic usage which might have applied to our humble brook which ranges from distinctly sluggish to briefly torrential.

A scan for similar names in England brings up the frequent occurrence of rivers named Blyth, Blithe or Blythe with nearby village names such as Blythburgh and Blyford (Suffolk), Blythe (Nr. Edinburgh and Newbiggin-on-Sea).  In Nottinghamshire there is a Blidworth with no apparent river, like Blisworth, but with a similar Domesday name to ours.  In the search, blith has also been interpreted as merry or gentle from the Old English.

The second half of the compound comes from OE worp pronounced worth.  This word can mean merely a fence but more commonly an enclosure, eg. within a village.  If it is qualifying a personal name then it means "the homestead of..." otherwise the safest interpretation is that it referred to a fenced enclosure but this could become simply a place or location.

We are left with the conclusion that our Blisworth name originates as a Viking-named homestead belonging to a Blida or a poetically named place given of  happy, timid, sluggish or gentle (for a stream) and healthy or merry attributes or, amusingly, a place belonging to someone with one of those as a nickname.  The middle option is best but one is inclined to cling to the last option with the idea that maybe the brook and the lias clay promoted cultivation of a certain "healthy" mushroom.

It should be borne in mind that frequently a stream may be named Blythe (merry, babbling, gentle etc.) - there is one such named in Fawsley parish.  Perhaps the original name was "Blida's homestead" but the pun with blithe would have possibly caught on, given the possibility our brook was once called Blythe or Blithe, so that the name effectively migrated to 'bliss-worth'.

Let's keep an open mind!