NoCGV Svalbard – photograph: Ministère des armées

The phrase to break the ice originally meant to make a beginning in an undertaking or enterprise, especially in the face of difficulty or resistance. (The sense evolution of the French phrase rompre, or briser, la glace has been identical.)

The underlying image is to break the frozen surface of a river, lake, etc., in order to make a passage for boats, etc.* This is clear from post-classical Latin scindere glaciem (the probable origin of the English and French phrases) as used by the Dutch humanist and scholar Desiderius Erasmus (circa 1469-1536) in Adagiorum chiliades (Thousands of adages – 1508), an annotated collection of Greek and Latin proverbs:

Scindere glaciem
Scindere glaciem est aperire viam et in incipiundo negocio priorem esse. Translatum a nautis, quorum unus aliquis praemittitur, qui flumine concreto glaciem praerumpat reliquisque viam aperiat.
     translation (from The Adages of Erasmus, selected by William Barker – University of Toronto Press, 2001):
To break the ice
To break the ice, is to open the way and to be the first in beginning a task. A figure derived from boatmen who send one of their number ahead to break up the ice on a frozen river and open the way for the others.

(William Barker remarks that, unlike most of the other adages in the book, this phrase is not found in classical literature; in Adagiorum collectanea (1500), Erasmus wrote that his source was the Italian humanist Francesco Filelfo (1398-1481), who used glaciem fregi, I have broken the ice.)

The earliest known use of to break the ice is from A treatis contayninge the lyfe and maner of death of that most holy prelat and constant martyr of Christ John Fysher Byshop of Rochester and Cardinall of the holy Church of Rome, composed from 1567 to 1577; this extract is about the opposition of John Fisher (1469-1535) to the divorce of Henry VIII from Catherine of Aragon:

(1891 edition)
There are verie fewe that can saye they have cleane escaped without feeling some part of the smart, so this reverend father tasted plentifully thereof, whom it chanced in the verie beginninge to be one of the first that brake the yse, and to open and shewe the inconvenient that followed therby: no doubt to his immortall fame and glorie, and no lesse to the reproach and ignominie of all such as were his persecutors, as by the sequell of this historie shall well appeare. I meane here of the divorce betweene kinge Henrie and queen Katherin his wife.

In the epilogue to A briefe treatise of testaments and last willes very profitable to be vnderstoode of all the subiects of this realme of England (London, 1591), the English ecclesiastical lawyer Henry Swinburne (circa 1551-1624) used the phrase in the sense to prepare the way for others:

The authour therefore in aduenturing to breake the yse to make the passage easie for his countrymen, failing sometimes of the fourd, and falling into the pit, may seeme worthie to be pitied.

The following passage from A pleasant conceited comedie, wherein is shewed, how a man may chuse a good wife from a bad (London, 1602), by the English playwright and poet Thomas Heywood (circa 1573-1641), shows the transition to the current sense, i.e. to relieve reserve, stiffness or shyness in a social setting:

– Mistris Arthur: My husband hath of late so much estrang’d
His words, his deeds, his heart from me,
That I can sildome haue his company:
And euen that sildome with such discontent,
Such frownes, such chidings, such impatience,
That did not truth & vertue arme my thoughts,
They would confound me with dispaire & hate,
And make me runne into extremities.
Had I deseru’d the least bad looke from him,
I should account my selfe too bad to liue,
But honouring him in loue and chastitie,
All iudgements censure freely of my wrongs.
                    Enter young Arthur, Maister Lusam, Pipkin.
– Young Arthur: Pipkin what said she when she sent for me?
– Pipkin: Faith maister she said little, but she thought more,
For she was very melancholy.
– Young Arthur: Did I not tell you she was melancholy?
For nothing else but that she sent for me,
And fearing I would come to dine with her.
– Maister Lusam: O you mistake her euen vpon my soule,
I durst affirme you wrong her chastitie.
See where she doth attend your comming home.
– Mistris Arthur: Come maister Arthur, shall we in to dinner?
Sirra be gone, and see it seru’d in.
– Maister Lusam: Will you not speake vnto her?
– Young Arthur: No not I, will you go in sir?
– Mistris Arthur: Not speak to me, nor once looke towards me?
It is my dutie to begin I know,
And I will breake this Ice of curtesie.
You are welcome home sir.

* The sense evolution of to break the ice is therefore comparable to that of to break ground, which means, literally, to do preparatory digging or other work prior to building or planting something, hence, figuratively, to do something innovative and beneficial.