In the following commentary we report underlying sales growth (abbreviated to ‘USG’ or ‘growth’) at constant exchange rates, excluding the effects of acquisitions and disposals.
https://www.unilever.com/Images/ir-q408-annou...

Underlying sales growth (USG), underlying volume growth (UVG), underlying price growth (UPG), underlying operating profit (UOP), underlying operating margin (UOM), underlying earnings per share (underlying EPS), constant underlying EPS, underlying effective tax rate, free cash flow (FCF) and net debt are non-GAAP measures (see pages 6 to 9). ...
Certain discussions and analyses set out in this announcement include measures which are not defined by generally accepted accounting principles (GAAP) such as IFRS. ...
Unilever uses 'constant rate', and 'underlying' measures primarily for internal performance analysis and targeting purposes. We present certain items, percentages and movements, using constant exchange rates, which exclude the impact of fluctuations in foreign currency exchange rates. ...
Underlying sales growth (USG)
Underlying Sales Growth or "USG" refers to the increase in turnover for the period, excluding any change in turnover resulting from acquisitions, disposals and changes in currency. ...
https://markets.ft.com/data/announce/full?doc...

It looked to me like the G ought to stand for 'growth.' I found the first link via a search on 'brand strength' plus the acronym, then other links that all point to an internally defined term at Unilever.

I can't vouch for it, but maybe you can tell if it fits your context.